Dental implants are placed in the jaw to provide support for a dental restoration, fixed bridge or removable partial denture. Dental implants provide good chewing function and also improve the patient's cosmetic appearance, thereby allowing the patient to smile, speak, and interact with others with greater confidence.
One type of dental implant widely used in the industry is a “threaded” implant. Threaded implants have an externally threaded body segment, which is screwed into a pre-drilled hole (i.e., an osteotomy), in the patient's upper or lower jawbone. Typically, the threaded implant body is formed with a central threaded socket accessible through the overlying gum tissue for receiving and supporting one or more dental attachments or components. Types of attachments and components that are received by the central socket include healing caps, impression copings and abutments. In turn, some of these attachments and components are useful to fabricate and/or to support a prosthodontic restoration, fixed bridge or partial denture. Exemplary implant constructions are disclosed in U.S. Pat. No. 4,645,453 to Nizick, U.S. Pat. No. 5,074,790 to Bauer and U.S. Pat. No. 5,312,255 to Bauer.
Dental implants are typically packaged as an assembly including all the tools necessary for the insertion of the implant into an osteotomy formed in the jaw. A typical threaded implant assembly includes a threaded implant body, an implant carrier, an insertion post, a coupling screw and a healing cap. The implant carrier, insertion post, and coupling screw are tools which are used for the insertion of the implant body. Typically, the implant carrier, insertion post and coupling screw are discarded after the implant body has been inserted into the osteotomy.
During the insertion procedure, the insertion post is securely coupled to the top of the implant body. The insertion post is held in place by a coupling screw, which traverses a central through-cavity in the insertion post and is threaded into the central threaded socket in the implant body. Typically, the bottom end of the insertion post has a hexagonal cavity that irrotationally mates with a hexagonal protrusion on the top of the implant, thereby preventing any relative rotation between the insertion post and implant body.
The coupling screw and insertion post are releasably coupled to an implant carrier. The implant carrier provides the dental practitioner with a means to grip and manipulate the assembly during the initial implantation procedure. Typically, the implant carrier includes a generally hexagonal internal passage at its bottom end which mates with a generally hexagonal outer surface of the insertion post. This allows torque applied to the carrier to be transferred, via the insertion post, to the threaded implant body. The dental practitioner uses the implant carrier to manipulate the implant body into the proper location within the jaw.
In use, the first step of the implantation procedure usually involves making an incision in the patient's gum. A portion of the gum is then folded back and an osteotomy is drilled in the jawbone. The diameter of the osteotomy is equal to or slightly smaller than the diameter of the implant body. The implant carrier is then used to transport the threaded implant assembly to the surgical site. The implant carrier is used by the practitioner to manipulate the implant body into the correct position and then to partially screw the implant body into the osteotomy. Once the implant body has been initially placed in the osteotomy and tightened manually, the carrier is then pulled and/or loosened and removed from the dental implant assembly, leaving only the insertion post and coupling screw in engagement with the threaded implant body. A suitable wrench or dental hand piece is then used to engage the insertion post and drive the implant to its final depth within the osteotomy. The coupling screw is then unscrewed from the implant body, thereby allowing extraction of the insertion post and coupling screw from the patient's mouth. Next, a healing cap is screwed into the exposed socket of the implant to cover the implant socket. The healing cap protects the implant socket against tissue in-growth during the initial healing period, and also prevents the entry of bacteria or other contaminants into the exposed central socket of the implant. Typically, the healing cap is housed in a cavity at the top of the implant carrier and is secured with a paper barrier until needed.
The insertion of the implant body and healing cap is followed by an initial healing period in which the bone is allowed to surround and retain the implant (i.e., “osseointegrate” with the implant) and the gum tissue is allowed to heal over the implant body and healing cap. For implants placed in the mandible, healing typically requires about three months; for implants in the maxilla, the healing period typically requires about six months.
After sufficient osseointegration has occurred, the gum tissue is re-opened by making an incision and the gum tissue is once again folded back to remove the healing cap from the implant body. To remove the healing cap from the implant body, torque is applied to the healing cap to rotate the healing cap out of the implant socket. Typically, a removal tool with a hexagonal tip is inserted into a corresponding mating hexagonal recess located in the top center of the healing cap. Great care must be used to rotate the healing cap without also rotating the implant body. Any movement of the implant body relative to the osteotomy during the removal of the healing cap could damage the osseointegration between the implant body and the jawbone. Damage to the osseointegration is very undesirable and could endanger the entire dental restoration process by destabilizing the implant. In addition, any movement of the implant body could create unwanted gaps or spaces between the implant body and jawbone which could lead to infection by bacteria or other contaminants. After the healing cap has been unscrewed and removed from the implant body, a suitable healing abutment is attached. The healing abutment extends through the gum tissue overlying the implant site.
A second healing period then ensues in which the gum tissue is allowed to heal around the post-osseointegration healing abutment. Typically, this second healing period lasts from four to eight weeks. After this second healing period, the healing abutment is removed from the implant. Typically, an impression is taken of the patient's mouth to fabricate a prosthesis or dental restoration. An abutment supporting the final restoration is attached to the implant. Lastly, the restoration is cemented or screwed to the abutment and/or implant to complete the placement of the prosthodontic restoration in the patient's mouth.
The threaded dental implants described above, as well as other dental implants, such as “cylindrical” implants, require healing periods of three to six months or more. In the meantime, it has been desirable in the past to provide patients with temporary partial dentures or full dentures until the final restoration is in place. However, mastication forces on conventional temporary partial dentures and full dentures can harm or otherwise irritate the gum tissues overlying conventional submerged implants, bone grafts or tissue grafts and/or can also disturb the implants.
Accordingly, methods and structures are needed to provide protection to subcutaneous implants and the adjacent tissues from impinging mastication forces and moments during the healing period.